This invention relates generally to the field of safety devices, and more particularly, is directed to a motorized smoke and fire damper which is designed to function upon detection of the presence of smoke or heat.
Fire dampers have long been employed in connection with air conditioning, heating and ventilating duct work systems for fire protection purposes to prevent the spread of fire within the duct work from one fire separation to an adjacent fire separation and from floor to floor. In this manner, safety devices have been provided which are automatically responsive to heat to contain a fire within the area of incidence. Most of the prior art types of fire dampers which have been commonly employed in building construction utilize an enclosing frame which is affixed directly to the duct system and a blade assembly operable within the frame which is suitable to close the duct opening defined within the frame. Blade assemblies of the horizontally pivoting type and of the interlocking curtain type are most popular and have been most commonly employed in prior art duct systems. Fusible elements are employed to maintain the blade assembly in the open position during all normal periods of use. Upon sensing high temperatures within the duct system, the fusible element fuses to thereby release its blade assembly to close the duct opening, thereby preventing the passage of heat and fire through the fire damper from one fire division to another.
Experience with the prior art fire damper designs has proved that the average fire damper installation as presently in use and as generally approved by applicable governmental agencies and insurance carriers will not quickly react to the presence of smoke. Rather, the dampers are responsive only to the build up of sufficient heat, a condition which causes considerable delay between the first incidence of fire and the operation of the fire damper. Additionally, there are many reported incidences of smoldering type fires which generate dangerous quantities of smoke, but which do not build up sufficient heat to actuate the presently available fire damper equipment.
Recently, tests have been conducted and investigations have been made under actual fire conditions using relatively sophisticated test instruments. It has been determined that in most instances, the buildings subject to fire become untenable from smoke long before they are untenable due to the elevated temperatures caused by a fire. Because of this added awareness, much thought has been given recently to personnel protection in buildings. In accordance with and as a direct result of these recent studies, safety from smoke considerations now form an important building design parameter. However, despite the knowledge that smoke can be a killer, to this date, no satisfactory system has been developed to actually rapidly react to the presence of smoke to prevent the further spread of smoke through building ductwork. Numerous smoke detection devices have been developed and these devices are quite reliable and are in general use. However, the prior art smoke detection systems as presently available, have until now, been employed only to trigger alarm systems to thereby warn the building's occupants of the presence of smoke. No system has heretofore been available to permit a detector of smoke or heat to also automatically trigger a building occupant protective system. By utilizing a motorized smoke and fire damper in accordance with the present invention and by wiring the device to a detector unit, fires can now be detected at early stages by the available smoke or products of combustion detection devices and the smoke dampers could be automatically activated through electrical stimuli generated by the detectors. In this manner, early detection can be utilized to function smoke dampers to prevent the spread of smoke in a building through the air conditioning, ventilating or heating duct systems.